Gear pumps are known for handling a variety of fluids in fluid systems. Gear pumps typically include a pair of externally toothed gears which are rotatably disposed within a pair of gear chambers. A drive shaft connected to one of the gears extends through an opening in the pump housing for rotation of the gears. The pump receives fluid at low pressure in a low-pressure port, and the gear teeth rotatingly intermesh to supply the fluid at a higher pressure through a high-pressure fluid port. The ports are typically oriented perpendicular to the rotational axis of the gears, although they can also be oriented parallel to the rotational axis of the gears.
Bearings and/or wear plates are provided on the opposite side surfaces of the gears, to facilitate rotation of the gears. The bearings and wear plates can be formed as separate components, or as unitary components. The bearings can also be incorporated into the cover plates. In any case, the drive gear rotates on the drive shaft supported radially by the drive gear bearings, and the driven gear rotates on a driven shaft supported radially by the driven gear bearings. The cover plates, bearings, and/or wear plates support the drive gear and driven gear axially in the pump body.
The pumped fluid is also used for lubrication of the bearings. To this end, a flow path is typically provided from the high-pressure fluid port to the bearings. Alternatively (or in addition), leakage is allowed between the opposing surfaces of the gears and bearings. In any event, the fluid lubricates the bearings and is then returned to the low-pressure fluid port such that the lubricating fluid is intermixed with the incoming fluid.
It is believed that one disadvantage of prior pumps is that the lubricating fluid is drawn off from the sides of the gears on the high pressure side of the pump, and then returned toward the sides of the gears on the lower pressure side of the pump. This tends to allow the returning fluid to flow down the side of the low pressure port, enter the gear teeth towards the sides of the gears, and then be drawn again through the recirculating flow path. In other words, the same fluid is used again and again for lubrication purposes. This can be undesirable, as the fluid removes heat from the bearings during lubrication, and if the fluid is caused to pass again and again through the bearings, the bearings can overheat, causing damage to the pump, and degrading the fluid. The recirculated fluid also degrades (shears) as it passes between the rotating gear and bearing surfaces, which can further degrade the fluid if it is passed again and again across these surfaces, as well as affect the over-all quality of fluid passing through the pump.
As such, it is believed that there is a demand in the industry for a new and improved gear pump which has a recirculating flow path for lubrication of the bearings, and which overcomes the disadvantages noted above such that the recirculated fluid is uniformly mixed into the incoming fluid.